Telematics units within mobile vehicles provide subscribers with connectivity to a telematics service provider (TSP). The TSP provides subscribers with an array of services ranging from emergency call handling and stolen vehicle recovery to diagnostics monitoring, global navigation system aided position identification, map services, and turn-by-turn navigation assistance. Telematics units are often provisioned and activated at a point of sale when a subscriber purchases a telematics-equipped vehicle. Upon activation, the telematics unit can be utilized to provide a subscriber with telematics services such as those described herein.
One telematics service provided by TSPs is a Global Navigation Satellite System (GNSS) based navigation service. GNSS is a generic term referring to any of multiple satellite constellation-based global positioning networks including, for example, the Global Positioning System (GPS) constellation. Another GNSS constellation network is the Global Navigation Satellite System (GLONASS). A particular example of a GNSS based navigation service is one providing turn-by-turn (TBT) directions to a telematics unit based upon a specified destination and current conditions including the current location of the telematics unit. Several other GNSS systems are currently under development and are capable of providing at least partial positioning functionality.
GNSS measurements are inherently noisy, and the measurement noise is difficult to model in advance due to environmental changes (e.g., open sky versus urban canyon) and/or variable satellite coverage. Without a reference position (i.e., the “real” position of the GNSS receiver), a navigation system cannot determine the degree of measurement error with respect to real-time measurements. This causes problems with respect to the provision of TBT directions and other navigation-related services to telematics subscribers—for example, indicating a subscriber is off-course relative to a driving route and recalculating driving directions when the subscriber is actually on-course.
The above body of information is provided for the convenience of the reader. The foregoing describes a suitable environment for which the described system and method are provided, and is not an attempt to review or catalog the prior art.